Authorities were tipped off Tuesday after a student at Mohegan High School in Clinton Township reported seeing a social media posting with threats of an attack at Henry Ford II High School in Sterling Heights, according to Sterling Heights police.

The attack would be similar to what happened in Florida and was going to occur Thursday, according to the threat.

McElrath is not a current or former student of Henry Ford II, police said.

School districts across metro Detroit — and the entire country — have seen a spike in threats following the Feb. 14 shooting at Marjory Stoneman Douglas High School in Parkland, Fla.

More than 130 threats were reported and analyzed by the USA TODAY NETWORK in the nine-day span after the shooting in Parkland left 17 dead. Also, non-profits such as the Educator's School Safety Network have compiled a list of the threats using news media reports. The group found that a jarring 638 threats targeted schools in the two weeks after the Parkland shootings, a number they say is probably on the low side.

Following the Florida rampage, panic swept schools from Maine to California, leading to lockdowns, school closures and deployment of bomb-sniffing dogs.

The dramatic rise in threats — from 10 to about 70 a day — has left school administrators and authorities walking a fine line in dealing with a threat's credibility. It's also worried parents who fear sending their children to school and shined a spotlight on the legal debate over what penalties kids should face.

At the root of the problem, experts say, are students who are too young to realize the severity of their comments.

"There are usually two common traits in these individuals," said Mary Ellen O'Toole, a former FBI profiler. "They're young, and their judgment is poor. I mean, a brain isn't really fully formed until your early 20s. Then, it's also people who want to be disruptive and affect how the school is operating."

Texas, with 55 reports, was the state with the most threats since the shooting. Next in line are Ohio, California, Florida and Pennsylvania, according to data from the Educator's School Safety Network, which not only tracks such incidents but also trains schools on how to handle them.

Because of the threats, at least 33 schools closed and more than 15 others locked down, according to a review of the incidents reported across the USA TODAY Network, which encompasses more than 100 news organizations nationwide.

Some threats were real and law enforcement was able to thwart the plot before it came to fruition, but the larger number of the scares weren't credible, meaning the person suspected of making the comments wasn't planning to harm others and didn't have access to weapons.

Recent threats have disrupted several schools in metro Detroit. In Washtenaw County, the sheriff's office has responded to nine threats against school districts over the last three weeks.

Macomb County Prosecutor Eric Smith has pledged to prosecute students who make threats.

"If you haven't done so already, I urge every parent, teacher and administrator to take time out of their day to discuss the rash of arrests that have occurred since the senseless tragedy in Parkland, Fla," he said. "Don't wait — have the discussion now."

At his arraignment, McElrath was given a $20,000 bond, with the option to post 10%, according to police. He was also ordered to wear a tether.